Sanyo N3000CR NiCad vs. A123

[johnws6]

All, i'm deciding which would be better for use on a re-design for my electric pocket bike. From the specs, the sanyo nicads look to have a lower resistance of 3.4 mohms and the a123 are 8 mohms. I just want to make sure im not overlooking anything, but wouldn't the sanyos hold their voltage comparably better than the a123s at say, 70 amps? Many people in the robot combat world have used these at 200 + amp rates, of course with no bms ( might get destroyed anyways) and they seem to hold up well.

Sanyo spec sheet: http://www.sanyo.co.jp/energy/english/spec/cadnica/N-3000CR.pdf

A12 spec sheet: http://www.a123systems.com/products

I currently have 300 of these N3000CR cells brand new, but im hesitant to assemble them all together into a 40s7p pack unless these would be better cells for my application. I'm currently running the met pmdc motor off of ebay with a logisystems 48 volt 700 amp controller.

Current motor: http://stores.ebay.com/M-R-MOTORSPORT-Spree-Gyro-Parts

 

[fechter]

The NiCd's look pretty good. In order to build a large pack, you need to separate the parallel strings for charging, which tends to be a hassle. With a large A123 pack, at least the pack can stay configured during charging, but you need a BMS.

There are some ways you could use diodes or FETs to separate the strings for charging with a NiCd so you can simply plug in the charger. Some kind of cell voltage monitoring system might be good too if you ever run them close to fully discharged.

I think either chemistry would be able to supply the current you need if the pack size is large enough.

A123's are probably much more expensive, but if properly treated should give more cycles.

 

[johnws6]

Separating the strings does seem to be one of the problems, especially since these prefer to be fast charged and there isn't many 48 volt 4 amp peak chargers. The astro 112D comes to mind, but that means i'd have 8 hours of charging, and would have to disconnect and charge each pack individually. I thought about using these 30 min bosch 24 volt chargers, but i would need 14 of them and need to break up the pack 14 ways.

 

[johnws6]

This might be the solution, it's a high current switch that lets the user switch between power and charging circuits. mc master carr part number 69685K61 The good news is i already have one of these laying around in the garage somewhere. Maybe something like this would work?